1. Field of the Invention
The present invention relates to swallowable capsule cameras. In particular, the present invention relates to methods the capsule camera to detect its own location.
2. Discussion of the Related Art
Devices for imaging body cavities or passages in vivo are known in the art and include endoscopes and autonomous encapsulated cameras. Endoscopes are flexible or rigid tubes that are passed into the body through an orifice or surgical opening, typically into the esophagus via the mouth or into the colon via the rectum. An image is taken at the distal end using a lens and transmitted optically to the proximal end located outside the body, either by a lens-relay system or by a coherent fiber-optic bundle. Alternatively, an instrument may record an image electronically at the distal end (e.g., using a CCD or CMOS array) and transfers the image data electrically to the proximal end through a cable. Endoscopes allow a physician control over the field of view and are well-accepted diagnostic tools. However, they have a number of limitations, present risks to the patient, and are invasive and uncomfortable for the patient. The cost of these procedures restricts their application as routine health-screening tools.
Because of the difficulty traversing a convoluted passage, endoscopes cannot reach the majority of the small intestines and special techniques and precautions—that increase cost—are required to reach the entirety of the colon. Endoscopic risks include the possible perforation of the bodily organs traversed and complications arising from anesthesia. Moreover, a trade-off must be made between patient pain during the procedure and the health risks and post-procedural down-time associated with anesthesia. Therefore, endoscopy is necessarily an in-patient service that involves a significant amount of time from clinicians and thus is a costly procedure.
An alternative in vivo image sensing technique is capsule endoscopy. In capsule endoscopy, a camera is housed in a swallowable capsule, along with a radio transmitter for transmitting data (which consists primarily of images recorded by the camera) to a base-station receiver or transceiver in a data recorder located outside the body. The capsule may also include a radio receiver for receiving instructions or other data from a base-station transmitter. Instead transmitting in a radio frequency, lower frequency electromagnetic signals may be used. Power may be supplied inductively from an external inductor to an internal inductor within the capsule or from a battery within the capsule.
An early example of a camera in a swallowable capsule is described in the U.S. Pat. No. 5,604,531, issued to the Ministry of Defense, State of Israel. A number of patents assigned to Given Imaging describe more details of such a system, using a transmitter to send the camera images to an external receiver. Examples are disclosed in U.S. Pat. Nos. 6,709,387 and 6,428,469. There are also a number of patents to the Olympus Corporation describing a similar technology. For example, U.S. Pat. No. 4,278,077 shows a capsule with a camera for the stomach, which includes film in the camera. U.S. Pat. No. 6,939,292 shows a capsule with a buffering memory, a timer, and a transmitter. U.S. Pat. No. 6,800,060 describes a swallow-able capsule camera that may be retrieved after passing from the body; that capsule camera uses an expensive and rare ultra-high-density atomic-resolution storage (ARS) medium to store images taken.
Introducing the capsule camera into a patient's body begins with removing the capsule from a package having a reed switch. While inside the package, a magnet keeps the reed switch in the capsule in the “off” position. In the “off” position, the capsule camera draws no power. Once removed from the package, the capsule is switched on, as the magnetic force is no longer holding back the metal spring that keeps the reed switch in the “off” position. The patient then swallows the capsule. In the prior art, another approach to activate the capsule camera includes providing a conductive liquid inside the capsule. By shaking the capsule strongly enough in the right direction, the conductive liquid causes contact be made an end of a pipe or chamber, which connects the system to a power source, so as to begin operation.
It is generally not necessary to take pictures when the capsule camera is outside the human body. Storing or transmitting pictures taken outside the body wastes power and takes up valuable space for archiving images. There are a few operations that a capsule camera may carry out prior to entering into the human body. For example, the capsule camera may perform a self-diagnostic to ensure that the system is fully functional. In addition, a reusable capsule camera may also communicate the number of times the capsule camera has been used inside a human body, so as to avoid introducing a capsule camera beyond the number of times it is designed to be used for. Alternatively, the capsule camera may be disposable (i.e., used only once).
From the mouth, the capsule camera enters the esophagus, then the stomach, the small intestines and the large intestines, in that order, before exiting the body. After it exits the body, no more images need to be taken. To image the large intestines, motility-enhancing drugs are typically used, so that the capsule camera may be able to traverse the entire GI tract within a reasonable amount of time, and particularly before the power needed for its operations is exhausted. In other words, it is desired that some power remains at the time the capsule camera exit the body. To cover the expected variations within the human population, the capsule camera must be provided power to allow a complete imaging for a very high percentage of people. Therefore, for most people, many images are taken by the capsule camera even after the capsule exits the body.
The storage requirement for the images is one problem current capsule endoscopy must overcome. The large size of a file created from the images taken from a human person is prohibitive for transmission over the Internet, and makes archiving and later retrieval difficult and costly. Another problem is cost. To have a technician review and edit out images in the file that are taken outside of the human body is costly. Further, a patient should be able to use the capsule camera at his/her home without privacy concerns, images taken outside the body should not be stored or transmitted.
Also, for a capsule camera in which on-board storage is provided for storing images, rather than transmitted by wireless, the capsule camera must be retrieved after it exits the body. A mechanism that facilitates retrieval after the capsule exits the body is desirable.
In light of the above, an automatic method for detecting when the capsule enters into and exits the body is desired, together with the ability for the capsule camera to distinguish its various modes of operations are desired.